Synnefo

# Copyright (C) 2010 Daniele Varrazzo <daniele.varrazzo@gmail.com>

# and licensed under the MIT license:

#

# Permission is hereby granted, free of charge, to any person obtaining a copy

# of this software and associated documentation files (the "Software"), to deal

# in the Software without restriction, including without limitation the rights

# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

# copies of the Software, and to permit persons to whom the Software is

# furnished to do so, subject to the following conditions:

#

# The above copyright notice and this permission notice shall be included in

# all copies or substantial portions of the Software.

#

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

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# THE SOFTWARE.

"""A wait callback to allow psycopg2 cooperation with gevent.

Use `make_psycopg_green()` to enable gevent support in Psycopg.

"""

import psycopg2

from psycopg2 import extensions

from gevent.socket import wait_read, wait_write

def make_psycopg_green():

    """Configure Psycopg to be used with gevent in non-blocking way."""

    if not hasattr(extensions, 'set_wait_callback'):

        raise ImportError(

            "support for coroutines not available in this Psycopg version (%s)"

            % psycopg2.__version__)

    extensions.set_wait_callback(gevent_wait_callback)

def gevent_wait_callback(conn, timeout=None):

    """A wait callback useful to allow gevent to work with Psycopg."""

    while 1:

        state = conn.poll()

        if state == extensions.POLL_OK:

            break

        elif state == extensions.POLL_READ:

            wait_read(conn.fileno(), timeout=timeout)

        elif state == extensions.POLL_WRITE:

            wait_write(conn.fileno(), timeout=timeout)

        else:

            raise psycopg2.OperationalError("Bad result from poll: %r" % state)